I had this... Its a bubble in your heater core and you need it flushed. It's cool, its covered by warranty.

 

i had the same thing for just a week
i dont know but i'm thinking it's coming from the air vent ??
i also have some tapping noise over my head and it's like coming from the back i couldn't find what it is and it's really annoying .
i will take it in to the dealership next week and have it checked out !